1. Field of the Invention
The present invention pertains to an implantable intraocular lens, and more particularly, pertains to a lens containing annular lens elements. The present invention relates to lenses which have discrete areas which serve to bring impinging rays to a focus in an specific area of the focal plane. Such lenses are called zone of focus lenses and are particularly useful for implantation into the eye as a substitute for the natural lens since, in combination with the brain, they effectively replicate the ability of the natural lens to bring objects at varying distances to a sharp focus.
The invention relates specifically to a zone of focus lens in which the lens is divided into annular lens elements. Each lens element serves to bring the impinging rays from an object at a predetermined distance to a focus on a particular region of the retina. By selecting various powers for the elements, it is possible to have an object at a given distance brought to an acceptable focus by at least one of such elements. In this manner, an in-focus image (sharp image) is created on a particular portion of the retina serviced by that element. It has been found that the processing of the image by the brain results in the selective consideration of the sharpest image and the virtual discard of the other out of focus images created by other elements.
2. Description of the Prior Art
Prior art includes limited attempts to produce a lens having areas of varying powers have been made. There have been many attempts to produce implantable lenses which serve for both close and far seeing, similar to the bifocal spectacles. In general, such lenses have been produced with two regions having different powers. The light which impinges on the retina passes through one region to the exclusion of the other. In such a system, only one region of the lens is used at a time and there is no accommodation by the brain to reject an out of focus image. Great care and accuracy must be used in the pre-operative measurements since both the near and far powers must be accurately determined. Since the near and far powers are not specifically interrelated, the inventory requirements are compounded since a variety of near powers must be available for every far power.
The present invention overcomes the disadvantages of prior art references by providing a lens which includes an annularly segmented lens where each segment is of a different power.